Price minus the broker fee, debt payoff, a working capital adjustment and transaction costs, stepped down to an estimated net at close.
Working capital adjustment: positive if you owe the buyer at close, negative if the buyer owes you.
An estimate, not tax or legal advice. How this proceeds figure is taxed depends on how the purchase price is allocated across asset classes (goodwill, equipment, inventory and so on), which both sides report on IRS Form 8594. This tool does not estimate a tax bill; that allocation is a negotiated part of the deal and worth an accountant's time before you sign anything.
Most purchase agreements set a target level of working capital the business needs to keep running. If the actual balance at close is below that target, you owe the buyer the difference; if it is above, the buyer owes you. The sign on this line depends on which side of the target you land on.
It does not include any tax owed on the sale. That depends on how the price is allocated across the business's asset classes, a negotiated item reported on IRS Form 8594, not something a calculator can estimate without your actual numbers and an accountant.